My opinion of Rockefeller changed a lot after reading his biography, "Titan". Philanthropy had been part of his life even as a child. He always gave something like 10-20% of his allowance to charity, and had stated that he intended to get as much money as possible IN ORDER TO give it away.
"The person who starts out simply with the idea of getting rich won't succeed; you must have a larger ambition."
"I know of nothing more despicable and pathetic than a man who devotes all the hours of the waking day to the making of money for money's sake."
I'm not saying he didn't do some shady crap to get what he did, but giving it away definitely wasn't an afterthought for him.